Method for producing polymer electrolyte membrane and polymer electrolyte membrane

Abstract

A method for continuously producing a polymer electrolyte membrane including: (i) a preparation step for preparing a polymer electrolyte solution by dissolving a polymer electrolyte containing an ion conductive polymer having an ion-exchange group in an organic solvent capable of dissolving the polymer electrolyte, (ii) a coating step for continuously obtaining a laminate film 1 wherein a supporting substrate and a layer containing an ion conductive polymer are laminated, by casting the polymer electrolyte solution obtained in the step (i) onto the continuously fed supporting substrate, and (iii) a drying step for continuously obtaining a laminate film 2 wherein the supporting substrate and a polymer electrolyte membrane intermediate are laminated, by removing the organic solvent remaining in the layer containing an ion conductive polymer with passing the laminate film 1 obtained in the step (ii) in a drying furnace; wherein the residence time of the laminate film 1 in the drying furnace in the step (iii) is 50 minutes or shorter and the remaining organic solvent concentration in the polymer electrolyte membrane intermediate in the laminate film 2 immediately after the laminate film 2 passes through the drying furnace is 40% by weight or lower.

1 . A method for continuously producing a polymer electrolyte membrane comprising:
 i) a preparation step for preparing a polymer electrolyte solution by dissolving a polymer electrolyte containing an ion conductive polymer having an ion-exchange group in an organic solvent capable of dissolving the polymer electrolyte,   (ii) a coating step for continuously obtaining a laminate film  1  wherein a supporting substrate and a layer containing an ion conductive polymer are laminated, by casting the polymer electrolyte solution obtained in said step (i) onto the continuously fed supporting substrate, and   (iii) a drying step for continuously obtaining a laminate film  2  wherein the supporting substrate and a polymer electrolyte membrane intermediate are laminated, by removing said organic solvent remaining in the layer containing an ion conductive polymer with passing the laminate film  1  obtained in said step (ii) in a drying furnace; wherein the residence time of the laminate film  1  in the drying furnace in said step (iii) is 50 minutes or shorter and the remaining organic solvent concentration in the polymer electrolyte membrane intermediate in the laminate film  2  immediately after the laminate film  2  passes through the drying furnace is 40% by weight or lower.   
     
     
         2 . The method for continuously producing a polymer electrolyte membrane according to  claim 1 , wherein said drying furnace has a heating zone of 60 to 130° C. 
     
     
         3 . The method for continuously producing a polymer electrolyte membrane according to  claim 1 , wherein the remaining organic solvent concentration in the layer containing an ion conductive polymer in the laminate film  1  immediately before the laminate film  1  comes in said drying furnace exceeds 70% by weight. 
     
     
         4 . The method for continuously producing a polymer electrolyte membrane according to  claim 1 , further comprising (iv) a winding step for winding the laminate film  2  obtained in the step (iii) on a winding core. 
     
     
         5 . The method for continuously producing a polymer electrolyte membrane according to  claim 1 , wherein said ion conductive polymer has an aromatic ring constituting the main chain and the ion-exchange group directly bonded or indirectly bonded through another atom or an atomic group to the aromatic ring constituting the main chain. 
     
     
         6 . The method for continuously producing a polymer electrolyte membrane according to  claim 1 , wherein the ion conductive polymer includes:
 one or more structure units having an ion-exchange group selected from the following (1a), (2a), (3a) and (4a),   
       
         
           
           
               
               
           
         
         wherein Ar 1  to Ar 9  each independently denote a divalent aromatic group having an aromatic ring constituting the main chain and optionally having a side chain having an aromatic ring and having an ion-exchange group directly bonded to at least one aromatic ring selected from the group consisting of the aromatic ring constituting the main chain or the aromatic ring in the side chain; Z and Z′ each independently denote —CO— or —SO 2 —; X, X′, and X″ each independently denote —O— or —S—; Y denotes a direct bond or a group defined by the following formula (100); p denotes 0, 1, or 2; and q and r each independently denote 1, 2, or 3, and one or more structure units having no ion-exchange group selected from the following (1b), (2b), (3b) and (4b), 
       
       
         
           
           
               
               
           
         
         wherein Ar 11  to Ar 19  each independently denote a divalent aromatic group optionally having a substituent group as a side chain; Z and Z′ each independently denote —CO— or —SO 2 —; X, X′, and x″ each independently denote —O— or —S—; Y denotes a direct bond or a group defined by the following formula (100); p′ denotes 0, 1, or 2; and q′ and r′ each independently denote 1, 2, or 3; 
       
       
         
           
           
               
               
           
         
         wherein R a  and R b  each independently denote a hydrogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, an optionally substituted alkoxy group having 1 to 10 carbon atoms, an optionally substituted aryl group having 6 to 18 carbon atoms, an optionally substituted aryloxy group having 6 to 18 carbon atoms, or an optionally substituted amyl group having 2 to 20 carbon atoms and R a  and R b  may be bonded with each other to form a ring in combination with the carbon atoms to which they are bonded. 
       
     
     
         7 . The method for continuously producing a polymer electrolyte membrane according to  claim 1 , wherein said ion conductive polymer is a copolymer including one or more blocks (A) having an ion-exchange group and one or more blocks (B) having substantially no ion-exchange group, and having block copolymerization or graft copolymerization mode. 
     
     
         8 . The method for continuously producing a polymer electrolyte membrane according to  claim 7 , wherein said ion conductive polymer includes a block in which the ion-exchange groups is directly bonded to the aromatic ring constituting the main chain as said blocks (A) having ion-exchange groups. 
     
     
         9 . The method for continuously producing a polymer electrolyte membrane according to  claim 7 , wherein said ion conductive polymer includes, as said blocks (A) having an ion-exchange group, a block represented by the following formula (4a′) 
       
         
           
           
               
               
           
         
         wherein Ar 9  is the same in above formula (4b) and m denotes a polymerization degree of the structure unit constituting the block) and, as the blocks (B) having substantially no ion-exchange group, one or more blocks selected from the following formulas (1b′), (2b′) and 
       
       
         
           
           
               
               
           
         
         wherein, Ar 11  to Ar 18  each independently denote a divalent aromatic group optionally having a substituent group as a side chain; n denotes a polymerization degree of the structure unit constituting the block; and other reference characters denote the same as described above. 
       
     
     
         10 . The method for continuously producing a polymer electrolyte membrane according to  claim 1 , wherein the polymer electrolyte membrane has a microphase-separated structure into at least two or more micro-phases. 
     
     
         11 . The method for continuously producing a polymer electrolyte membrane according to  claim 10 , wherein said ion conductive polymer is a copolymer including one or more blocks (A) having an ion-exchange group and one or more blocks (B) having substantially no ion-exchange group, having block copolymerization or graft copolymerization mode and said polymer electrolyte membrane includes a microphase-separated structure containing a phase in which density of the blocks (A) having an ion-exchange group is higher than that of the blocks (B) having substantially no ion-exchange group, and a phase in which density of the blocks (B) having substantially no ion-exchange group is higher than that of the blocks (A) having an ion-exchange group. 
     
     
         12 . The method for continuously producing a polymer electrolyte membrane according to  claim 1 , wherein said ion conductive polymer has a sulfonic acid group as the ion-exchange group. 
     
     
         13 . A polymer electrolyte membrane obtained by the production method according to  claim 1 . 
     
     
         14 . A membrane electrode assembly comprising the polymer electrolyte membrane according to  claim 13 . 
     
     
         15 . A fuel cell comprising the membrane electrode assembly according to  claim 14 .